Annular barriers are often expanded downhole by means of pressurised fluid entering through an opening in the pipe around which the annular barrier extends, however, operators of oil wells are increasingly demanding that this opening is permanently closed.
One solution to this problem has been to insert check valves in the opening, however, this solution has shown to fail as dirt may get stuck in the ball seat, thereby preventing the ball from closing the opening properly. Further, as temperature and pressure increase and decrease, e.g. during a fracturing process, the temperature and pressure of the entrapped fluid in the annular barrier increase and decrease accordingly. During increased pressure, the annular barrier is expanded more than intended, and during decreasing pressure, the annular barrier deflates accordingly, and such movements may rupture the annular barrier over time.